1. Field of the Invention
The present invention relates to an optical position tracking device and, more particularly, to an optical position tracking device having a self-test function, which does not exclusively employ a test apparatus, and a method of testing the same.
2. Description of Related Art
A position tracking device, which is a kind of computer input device, is used to directly or indirectly indicate the coordinates of a cursor or a pointer on a computer. Position tracking devices may be largely classified into a ball position tracking device and an optical position tracking device. The ball position tracking device rotates a ball and inputs a moving direction and distance of the ball. The optical position tracking device tracks the motion of a surface image created by light emitted from a light source of a position tracking unit and detects a moving direction and distance of the surface image.
The optical position tracking device does not mechanically detect the operation of the ball. Instead, the optical position tracking device lights the surface of a worktable to reflect light emitted from the light source of the position tracking unit to create a surface image, consecutively captures the surface image at high speed to compare sequentially captured surface images, and detects a moving direction and distance of the surface image. Thus, the optical position tracking device optically recognizes the motion of a contact object, converts a recognized value into an electrical signal, and transmits the electrical signal to a computer, so that the position of a cursor can be displayed on a monitor.
FIG. 1 is a block diagram of a conventional optical position tracking device.
Referring to FIG. 1, an optical position tracking device 100 includes an image sensor 110 having a plurality of pixels, an analog-to-digital converter (ADC) 120, a logic unit 130, a frequency generator 140, an illumination unit 150, and a lens 160. The logic unit 130 includes a position tracking module 132, an interface portion 134, and an input portion 136. The lens 160 allows light, which is irradiated by the illumination unit 150 and reflected from the surface of a worktable, to travel toward the image sensor 110 having the pixels. The light irradiated by the illumination unit 150 travels in the arrow direction shown in FIG. 1.
Functions and operations of the respective blocks shown in FIG. 1 will now be described.
The image sensor 110 having the pixels receives light reflected from the surface of the worktable through the lens 160, senses an image of an object, and outputs an analog signal corresponding to the sensed image.
The ADC 120 receives the analog signal from the image sensor 110 and converts the analog signal to a digital signal.
The converted digital signal is applied to the position tracking module 132 of the logic unit 130. The position tracking module 132 is synchronized with a clock signal, which is periodically output from the frequency generator 140, calculates a motion value corresponding to the converted digital signal, and outputs a coordinate signal.
The input portion 136 includes a button or a scroll apparatus and outputs an input signal in response to a user's manipulation.
The interface portion 134 outputs motion information INF to an external device, such as a computer, in response to the input signal and the coordinate signal.
The illumination unit 150 may include a light source, which irradiates light to the surface of the worktable, and a control circuit, which turns on or off the light source. The light source may be a light emitting diode (LED).
In order to confirm whether the optical position tracking device including the above-described components operates normally, a test is conducted on the optical position tracking device. In general, the image sensor 110, the ADC 120, the position tracking module 132, and the frequency generator 140 are tested.
FIG. 2 is a block diagram of a conventional optical position tracking device 100 and a test apparatus 300, which are provided separately.
The testing apparatus 300 includes a controller 310, which is used to control a test operation, a test signal generator 330, which outputs a test signal, and an output signal analyzer 350, which analyzes a signal output from an apparatus 100 and determines whether or not the apparatus is normal.
FIG. 2 illustrates the optical position tracking device 100 including only an image sensor 110, an ADC 120, a position tracking module 132, and a frequency generator 140 for brevity, although the optical position tracking device 100 further includes other components.
The controller 310 outputs a test start signal Ts_sig to perform a test on at least one of the image sensor 110, the ADC 120, the position tracking module 132, and the frequency generator 140 included in the optical position tracking device 100.
The test signal generator 330 receives the test start signal Ts_sig and outputs test signals T_sig1 to T_sig4 required for testing the respective apparatuses 110 to 140. The image sensor 110, the ADC 120, the position tracking module 132, and the frequency generator 140 generate output signals O_sig1 to O_sig4 in response to the corresponding test signals T_sig1 to T_sig4, respectively.
The output signals O_sig1 to O_sig4 are applied to the output signal analyzer 350 of the test apparatus 300. The output signal analyzer 350 compares each of the output signals O_sig1 to O_sig4 with an ideal signal, which is expected to be output by the corresponding one of the image sensor 110, the ADC 120, the position tracking module 132, and the frequency generator 140, determines whether or not each of the image sensor 110, the ADC 120, the position tracking module 132, and the frequency generator 140 is normal, and transmits a result signal Re_sig to the controller 310 based on the determination result.
Since the optical position tracking device 100 includes circuits, such as the image sensor 110 having a plurality of pixels, the ADC 120, and the position tracking module 132, and operates in response to various signals, the optical position tracking device 100 requires a high-performance test apparatus for generating the various signals. Also, an input signal required for testing the image sensor 110 is a light-type image signal, which is produced by reflecting light irradiated from an illumination unit by an object. Therefore, during a test operation, a variety of optical signals should be applied to the image sensor 110 using an additional apparatus instead of directly inputting the input signal to the image sensor 110. As a result, it takes much time to test the image sensor 110.
Furthermore, the conventional optical position tracking device 100 may further include an external system, which applies an analog signal to the ADC 120 and confirms an output signal of the ADC 120 in order to test the ADC 120. Also, test pins or test pads for applying an additional test signal are needed to test a plurality of circuits.